Killing "System Error" dialog box under csrss.exe

I'm running an automated test of an application that has insufficient dependencies (missing dll), and got this error message:

When the test runner kills the application, the above message box isn't disappearing. Apparently it's owned by csrss.exe, which can't be killed.

My problem is that the only way I can get this message box to close is by manually logging in to to the machine and clicking the X on that message window. Is there another way?

Note that I can easily fix the dependency error, but I would like a robust way of terminating the application under test with all its messages when such errors are encountered.